[pve-devel] [PATCH common v3 1/2] systemd: add sd_notify() helper

[Fiona Ebner]

Implement a pure Perl reimplementation of systemd's sd_notify() as
defined in systemd/sd-daemon.h, see also 'man 3 sd_notify'.

The initial user of this helper is intended to be the pve-dbus-vmstate
service, so it can notify startup completion only once the
dbus-vmstate QEMU object is ready to be used.

EAGAIN is not checked for, because it does not occur for blocking
Unix domain sockets, see 'man 2 send'.

Co-developed-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---

Changes in v3:
* Expand commit message.
* Use $socket->{send,shutdown) methods.
* Print $IO::Socket::errstr in case of error.
* Unset NOTIFY_SOCKET environment variable only after sending the
  message.

 src/PVE/Systemd.pm | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/src/PVE/Systemd.pm b/src/PVE/Systemd.pm
index e6d6f88..d0a291d 100644
--- a/src/PVE/Systemd.pm
+++ b/src/PVE/Systemd.pm
@@ -3,9 +3,12 @@ package PVE::Systemd;
 use strict;
 use warnings;
 
+use IO::Socket::UNIX;
 use Net::DBus qw(dbus_uint32 dbus_uint64 dbus_boolean);
 use Net::DBus::Callback;
 use Net::DBus::Reactor;
+use POSIX qw(EINTR);
+use Socket qw(SOCK_DGRAM);
 
 use PVE::Tools qw(file_set_contents file_get_contents trim);
 
@@ -282,4 +285,32 @@ sub write_ini {
     file_set_contents($filename, $content);
 }
 
+# This is a pure Perl reimplementation of systemd's sd_notify() as defined in systemd/sd-daemon.h
+sub sd_notify {
+    my ($unset_environment, $state) = @_;
+
+    my $socket_path = $ENV{NOTIFY_SOCKET};
+
+    my $socket = IO::Socket::UNIX->new(
+        Type => SOCK_DGRAM(),
+        Peer => $socket_path,
+    ) or die "unable to connect to socket $socket_path to notify systemd - $IO::Socket::errstr\n";
+
+    # we won't be reading from the socket
+    $socket->shutdown(SHUT_RD);
+
+    my $sent = 0;
+    my $total = length($state);
+    while ($sent < $total) {
+        my $res = $socket->send($state);
+        die "sending to $socket_path failed - $!" if !$res && $! != EINTR;
+        $sent += $res if $res;
+    }
+    $socket->flush();
+
+    close($socket);
+
+    delete($ENV{NOTIFY_SOCKET}) if $unset_environment;
+}
+
 1;
-- 
2.47.3